Re: [dpdk-dev] [PATCH] pci: keep API compatibility with mmap values

[David Marchand <david.marchand@redhat.com>]

On Fri, Jul 10, 2020 at 1:53 PM Thomas Monjalon <thomas@monjalon.net> wrote:
>
> The function pci_map_resource() returns MAP_FAILED in case of error.
> When replacing the call to mmap() by rte_mem_map(),
> the error code became NULL, breaking the API.
> This function is probably not used outside of DPDK,
> but it is still a problem for two reasons:
>         - the deprecation process was not followed
>         - the Linux function pci_vfio_mmap_bar() is broken for i40e
>
> The error code is reverted to the Unix value MAP_FAILED.
> Windows needs to define this special value (-1 as in Unix).
> After proper deprecation process, the API could be changed again
> if really needed.
>
> Because of the switch from mmap() to rte_mem_map(),
> another part of the API was changed: "int additional_flags"
> are defined as "additional flags for the mapping range"
> without mentioning it was directly used in mmap().
> Currently it is directly used in rte_mem_map(),
> that's why the values rte_map_flags must be mapped (sic) on the mmap ones
> in case of Unix OS.
>
> These are side effects of a badly defined API using Unix values.
>
> Bugzilla ID: 503
> Fixes: 2fd3567e5425 ("pci: use OS generic memory mapping functions")
> Cc: talshn@mellanox.com
>
> Reported-by: David Marchand <david.marchand@redhat.com>
> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> ---
>  drivers/bus/pci/bsd/pci.c                 | 2 +-
>  drivers/bus/pci/linux/pci_uio.c           | 2 +-
>  drivers/bus/pci/linux/pci_vfio.c          | 4 ++--
>  drivers/bus/pci/pci_common_uio.c          | 2 +-
>  lib/librte_eal/include/rte_eal_paging.h   | 8 ++++++++
>  lib/librte_eal/windows/include/sys/mman.h | 9 +++++++++
>  lib/librte_pci/rte_pci.c                  | 1 +
>  lib/librte_pci/rte_pci.h                  | 2 +-
>  8 files changed, 24 insertions(+), 6 deletions(-)
>  create mode 100644 lib/librte_eal/windows/include/sys/mman.h
>
> diff --git a/drivers/bus/pci/bsd/pci.c b/drivers/bus/pci/bsd/pci.c
> index 8bc473eb9a..6ec27b4b5b 100644
> --- a/drivers/bus/pci/bsd/pci.c
> +++ b/drivers/bus/pci/bsd/pci.c
> @@ -192,7 +192,7 @@ pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
>         mapaddr = pci_map_resource(NULL, fd, (off_t)offset,
>                         (size_t)dev->mem_resource[res_idx].len, 0);
>         close(fd);
> -       if (mapaddr == NULL)
> +       if (mapaddr == MAP_FAILED)
>                 goto error;
>
>         maps[map_idx].phaddr = dev->mem_resource[res_idx].phys_addr;
> diff --git a/drivers/bus/pci/linux/pci_uio.c b/drivers/bus/pci/linux/pci_uio.c
> index b622001539..097dc19225 100644
> --- a/drivers/bus/pci/linux/pci_uio.c
> +++ b/drivers/bus/pci/linux/pci_uio.c
> @@ -345,7 +345,7 @@ pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
>         mapaddr = pci_map_resource(pci_map_addr, fd, 0,
>                         (size_t)dev->mem_resource[res_idx].len, 0);
>         close(fd);
> -       if (mapaddr == NULL)
> +       if (mapaddr == MAP_FAILED)
>                 goto error;
>
>         pci_map_addr = RTE_PTR_ADD(mapaddr,
> diff --git a/drivers/bus/pci/linux/pci_vfio.c b/drivers/bus/pci/linux/pci_vfio.c
> index fdeb9a8caf..07e072e13f 100644
> --- a/drivers/bus/pci/linux/pci_vfio.c
> +++ b/drivers/bus/pci/linux/pci_vfio.c
> @@ -566,7 +566,7 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
>                 }
>
>                 /* if there's a second part, try to map it */
> -               if (map_addr != NULL
> +               if (map_addr != MAP_FAILED
>                         && memreg[1].offset && memreg[1].size) {
>                         void *second_addr = RTE_PTR_ADD(bar_addr,
>                                                 (uintptr_t)(memreg[1].offset -
> @@ -578,7 +578,7 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
>                                                         RTE_MAP_FORCE_ADDRESS);
>                 }
>
> -               if (map_addr == NULL) {
> +               if (map_addr == NULL || map_addr == MAP_FAILED) {
>                         munmap(bar_addr, bar->size);
>                         bar_addr = MAP_FAILED;
>                         RTE_LOG(ERR, EAL, "Failed to map pci BAR%d\n",
> diff --git a/drivers/bus/pci/pci_common_uio.c b/drivers/bus/pci/pci_common_uio.c
> index 793dfd0a7c..f4dca9da91 100644
> --- a/drivers/bus/pci/pci_common_uio.c
> +++ b/drivers/bus/pci/pci_common_uio.c
> @@ -58,7 +58,7 @@ pci_uio_map_secondary(struct rte_pci_device *dev)
>                                         "Cannot mmap device resource file %s to address: %p\n",
>                                         uio_res->maps[i].path,
>                                         uio_res->maps[i].addr);
> -                               if (mapaddr != NULL) {
> +                               if (mapaddr != MAP_FAILED) {
>                                         /* unmap addrs correctly mapped */
>                                         for (j = 0; j < i; j++)
>                                                 pci_unmap_resource(
> diff --git a/lib/librte_eal/include/rte_eal_paging.h b/lib/librte_eal/include/rte_eal_paging.h
> index ed98e70e9e..680a7f2505 100644
> --- a/lib/librte_eal/include/rte_eal_paging.h
> +++ b/lib/librte_eal/include/rte_eal_paging.h
> @@ -3,6 +3,7 @@
>   */
>
>  #include <stdint.h>
> +#include <sys/mman.h>
>
>  #include <rte_compat.h>
>
> @@ -22,6 +23,7 @@ enum rte_mem_prot {
>
>  /** Additional flags for memory mapping. */
>  enum rte_map_flags {
> +#ifdef RTE_EXEC_ENV_WINDOWS
>         /** Changes to the mapped memory are visible to other processes. */
>         RTE_MAP_SHARED = 1 << 0,
>         /** Mapping is not backed by a regular file. */
> @@ -35,6 +37,12 @@ enum rte_map_flags {
>          * it is not required to do so, thus mapping with this flag may fail.
>          */
>         RTE_MAP_FORCE_ADDRESS = 1 << 3
> +#else /* map mmap flags because they are exposed in pci_map_resource() API */
> +       RTE_MAP_SHARED = MAP_SHARED,
> +       RTE_MAP_ANONYMOUS = MAP_ANONYMOUS,
> +       RTE_MAP_PRIVATE = MAP_PRIVATE,
> +       RTE_MAP_FORCE_ADDRESS = MAP_FIXED,
> +#endif
>  };
>
>  /**
> diff --git a/lib/librte_eal/windows/include/sys/mman.h b/lib/librte_eal/windows/include/sys/mman.h
> new file mode 100644
> index 0000000000..0b4b10df1f
> --- /dev/null
> +++ b/lib/librte_eal/windows/include/sys/mman.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright 2020 Mellanox Technologies, Ltd
> + */
> +
> +/*
> + * The syscall mmap does not exist on Windows,
> + * but this error code is used in a badly defined DPDK API for PCI mapping.
> + */
> +#define MAP_FAILED ((void *) -1)
> diff --git a/lib/librte_pci/rte_pci.c b/lib/librte_pci/rte_pci.c
> index d8272b9076..1d1cbc75ac 100644
> --- a/lib/librte_pci/rte_pci.c
> +++ b/lib/librte_pci/rte_pci.c
> @@ -163,6 +163,7 @@ pci_map_resource(void *requested_addr, int fd, off_t offset, size_t size,
>                         __func__, fd, requested_addr, size,
>                         (unsigned long long)offset,
>                         rte_strerror(rte_errno), mapaddr);
> +               mapaddr = MAP_FAILED; /* API uses mmap error code */
>         } else
>                 RTE_LOG(DEBUG, EAL, "  PCI memory mapped at %p\n", mapaddr);
>
> diff --git a/lib/librte_pci/rte_pci.h b/lib/librte_pci/rte_pci.h
> index 104b2bb858..a03235da1f 100644
> --- a/lib/librte_pci/rte_pci.h
> +++ b/lib/librte_pci/rte_pci.h
> @@ -160,7 +160,7 @@ int rte_pci_addr_parse(const char *str, struct rte_pci_addr *addr);
>   *      The additional flags for the mapping range.
>   * @return
>   *   - On success, the function returns a pointer to the mapped area.
> - *   - On error, NULL is returned.
> + *   - On error, MAP_FAILED is returned.
>   */
>  void *pci_map_resource(void *requested_addr, int fd, off_t offset,
>                 size_t size, int additional_flags);
> --
> 2.27.0
>

As we discussed offlist, I am not really ecstatic about this.
But the function was exposed, so no breaking.

Reviewed-by: David Marchand <david.marchand@redhat.com>

-- 
David Marchand